1. Field of the Invention
The present invention relates to a velocity calculating device, a velocity calculating method, and a navigation device, which are suitable for, for example, a portable navigation device.
2. Description of the Related Art
Existing navigation devices receive position signals (hereinafter referred to as GPS signals) from a plurality of global positioning system (GPS) satellites and calculate the present position of a vehicle on the basis of the GPS signals.
However, when a vehicle in which the navigation device is placed is in a tunnel or an underground parking garage, it is difficult for the navigation device to receive GPS signals from GPS satellites and to calculate the present position on the basis of the GPS signals.
Even when it is difficult to receive GPS signals, some navigation devices calculate the velocity in the direction of travel of the vehicle on the basis of the acceleration in a horizontal direction perpendicular to the direction of travel and the angular velocity around the vertical axis perpendicular to the direction of travel when the vehicle is cornering, and thereby calculate the present position of the vehicle on the basis of the velocity in the direction of travel (see, for example, Japanese Unexamined Patent Application Publication No. 2008-76389).